The present invention relates to a ball retainer for a linear guide apparatus of a type that a slider hangs over a guide rail to freely move with respect to the guide rail through the rolling movements of balls. In particular, the present invention relates to an improved ball retainer which is mounted within the slider for holding the balls.
A conventional ball retainer of this type for a linear guide apparatus is disclosed in U.S. Pat. No. 4,929,095. As shown in FIG. 8, in a linear guide apparatus into mounting the ball retainer 5 therein, a guide rail 1 includes two ball rolling grooves 3 formed in a middle portion of a rail side surface 1b and an upper end portion (that is, a rail ridge portion 1c), respectively. In the linear guide apparatus, a large number of balls B are rollingly guided by the ball rolling groove 3 of the guide rail ridge portion 1c and a ball rolling groove 4 formed in the inner surface of a slider 2 opposed to the ball rolling groove 3. The ball retainer 5 holds the balls B so as to prevent them from falling away from the ball rolling groove 3 when the slider 2 is removed from the guide rail 1. And, the ball retainer 5 is disposed in a space within a recessed portion of the slider 2 hanging over the guide rail 1, particularly, the space being formed between an upper surface 1a of the guide rail 1 and an inner surface 2a of the slider 2 opposed to the guide rail upper surface 1a.
The ball retainer 5 has a planar shape which is similar to a substantially rectangular frame shape, as shown in FIG. 9. The ball retainer 5 includes two engaging portions 6 which are respectively formed in the longitudinal ends of the frame shape to project in the axial direction thereof. The ball retainer 5 also includes two ball hold grooves 7 which are respectively formed in both side edges of the frame shape and arc-shaped in cross section as shown in FIG. 10. In order to mount the ball retainer 5 into the slider 2, the engaging portions 6 are fitted into insertion recessed portions (not shown) formed in connecting end faces of two end caps 2B which are respectively connected to both ends of the slider 2.
On the other hand, in a wire shape is formed a ball retainer 5A for holding the balls B which exist within the ball rolling groove 4 below the slider 2 shown in FIG. 8. Further, the ball retainer 5A is such structured that, when the slider 2 is assembled to the guide rail 1, the ball retainer 5A can be received into a retainer escape groove 8 formed in the bottom surface of the ball rolling groove 3 formed in the side surface 1b of the guide rail 1. In FIG. 8, a hole 9 is formed in the guide rail 1 for a rail mounting bolt.
On the other hand, U.S. Pat. No. 4,918,846 has disclosed a dustproof seal in which a seal member contacting slidingly the upper surface of the guide rail is disposed in substantially the same portion as the above-mentioned ball retainer within the recessed portion in the slider and a seal (an inner seal) is disposed within the slider, so that the seal member prevents foreign matter from entering into the ball rolling groove of the slider. Such an inner seal is effective especially for a linear guide apparatus which is used in a dusty atmosphere. That is, dust is easy to collect in a cavity which is formed in the head portion of the guide rail mounting bolt to locate slightly lower than the rail surface. The dust collecting in the cavity passes through two side seals, which are generally mounted on the two end faces of the slider, and enters into the slider. If the dust collects only a little, then there arises no problem. However, if the amount of the collecting dust is large, then the entered dust attaches to the ball rolling grooves 3, 4 and balls B to thereby apply an obstacle to the operation of the linear guide apparatus.
The inner seal effectively seals between the rail upper surface and ball rolling grooves 3, 4 to prevent the dust from entering into them.
However, the conventional ball retainer 5 disclosed in the above-mentioned U.S. Pat. No. 4,929,095 is a single function device which is only able to hold the balls B within the upper ball rolling groove 4 in the slider 2. Therefore, there is a problem which it is not able to prevent the foreign matter from entering into the ball rolling grooves 3, 4.
On the other hand, the conventional inner seal disclosed in the above-mentioned U.S. Pat. No. 4,918,846 is also a single function seal which has only the sealing function but does not have the ball hold function. For this reason, especially when the inner seal is mounted in the slider of a linear guide apparatus of a type that the upper ball rolling grooves 3 of the guide rail 1 is formed in the rail ridge portion 1c as shown in FIG. 8, then there arises a problem which it is not possible to hold the balls within the upper ball rolling groove on the slider side corresponding to the ball rolling groove formed in the rail ridge portion.